Summer 2008 saw the grouping of Norwich’s premiere heritage buildings into a new organisation known as the Norwich 12. Representing an outstanding collection of Norwich’s iconic heritage buildings and spanning the last millennium, the group includes cathedrals, historic halls, a castle and more.

Heritage Open Days (HODs) runs every September, with special events and openings at historic properties, galleries and museums. Norwich’s wide-ranging programme offers free public access to places that are normally off limits or where entry fees are normally charged. With this in mind, 24 Hour Museum takes a sneaky look inside some of the Norwich 12 buildings that regularly open their doors for HODs.

From the medieval period until the late 18th century, Norwich was England’s second city, rich in mercantile wealth. The Normans arrived in Norwich in 1066 and began building the castle that stands today. Soon after Norman rule ceased, Richard I granted Norwich city status.

The next five centuries of medieval life would see the creation of one of the world’s most highly regarded heritage cities. As peasants revolted, knights crusaded and the Church of England was born, Norwich slowly gained a collection of streets and buildings that were to become world renowned.

1. Our trail begins with Norwich’s famous Guildhall. Situated in the city centre, the striking flint building looms over the market place reminding us of Norwich’s medieval roots. The centre of city government from the early 15th century until 1938, the building has housed various courts, a prison and a chapel.

HODs offers a rare opportunity to explore beyond Caley’s coffee shop on the ground floor. Book your place on a Blue Badge tour, where a guide will lead you around the rest of the building.

Reaching the top of the stairs is like taking a step back in time. Suddenly you are standing in a regal waiting room facing doors that lead to the grand Council Chamber and mysterious Sword Room.

The elaborate Council Chamber (or Mayor’s Court) boasts renaissance decorative woodwork and stunning stained glass. The oak panelling and a sixteen-bay roof with tie-beams were clearly designed to impress.

Across the hall, follow in the footsteps of medieval councillors as you enter the Sword Room whereupon you are hit by the dark oak and atmospheric aura. Today we can see a virtually intact late-Victorian courtroom with a roof space which was once the storage place of weapons such as swords.

HODs tours even take you underneath the building into an undercroft that pre-dates the Guildhall itself. Thought to be an original feature of the earlier toll-house on this site, it has also been used to hold dangerous criminals.

2. Returning, blinking into the daylight of the vibrant Market Place, our tour moves on and just a few minutes walk from the Guildhall, we reach Norwich’s 900 year old Castle.

The Castle hosts a wealth of collections - and you can usually make the most of the chance to explore them for free by dropping in during the HODs weekend.

There is the chance to enter the castle’s original keep with its great Norman arches and high balcony. Here you will encounter instruments of torture, or look down into the prison cells and view castle life through a giant doll’s house model.

Carrying on into the more modern part of the museum, you will discover Egyptian mysteries – why doesn’t the mummy’s body fit its case? In the Anglo Saxon and Viking Gallery you will meet Edmund, King of East Anglia from the year 855. There are also Iceni treasures galore and Saxon costumes to try on.

Look around the art galleries, taking in an eclectic mix of traditional and contemporary art, before joining a battlements and dungeons tour. Plaster death masks bring to life hanged Victorian criminals, while you learn of extraordinary stories and the history of crime and punishment. As you leave the castle, stop to look around the fabulous grounds and download some free facts and pictures from the new Bluetooth totem.

3. Following your HODs guide map, you may then choose to walk slightly outside of the city centre to find the Great Hospital. An exceptional set of medieval buildings, the hospital has been in continuous use for more than 750 years.

This is the only English medieval hospital whose archives and fabric together survived the dissolution of the monasteries. Take the chance to walk through the cloisters, which resemble those of a monastery or priory.

Entering the part of the hospital known as Eagle Ward, you will find St Helen's church with its ceiling dating from 1383 decorated with 252 painted black eagles. Moving on, you will discover a medieval refectory and a Victorian hall, as well as St Helen's House, built by Thomas Ivory in the 18th century.

Today, the Great Hospital continues to provide sheltered housing and care for the citizens of Norwich. Scheduled tours are usually available with prebooking during HODs.

4. Heading back to the city centre, you will soon reach The Forum. This is Norwich 12’s youngest member built to celebrate the new millennium. Nevertheless, the Forum is rich in history. Walk through the door and you are travelling over what was a pre-conquest settlement.

Today you will be struck by the vibrancy that fills the bright spacious building. Home to art displays, entertainments, BBC East, Norwich Tourist Information Centre, restaurants, and the Norfolk and Norwich Millennium Library, there is lots to explore.

Perhaps you will choose to visit the library, where a talk on 400 years of the old city library and a children’s stories of the past session will be held during HODs.

Each year during HODs you can explore these and more venues than the handful previewed on our trail, as well as a further range of museums, galleries and historic buildings taking part in HODs.

Brochures for HODs are available from the Guildhall Lobby, Norwich Tourist Information Centre and Norfolk Libraries. Alternatively, you can download a copy nearer the time from www.heritagecity.org.

Every year there are thousands of things happening for Heritage Open Days throughout the UK. Find out what's happening near you at www.heritageopendays.org.uk.

Katie Brinkley is the 24 Hour Museum/Norwich HEART Student Writer in Norwich. Norwich Heritage Economic and Regeneration Trust (HEART) is the groundbreaking initiative to regenerate, manage and promote one of the most remarkable heritage resources in the UK and in Europe.